Multichannel Chromogenic and Chiral Anions Recognition by Imidazolium Functionalized BINOL Derivatives

New imidazolium/benzimidazolium‐containing receptors ( R )‐ 1– ( R )‐ 6 were developed as multifunctional receptors for both chromogenic and chiral anion recognition through multichannel. The ?uorescence spectra of ( R )‐ 1 showed a distinct and intense peak at 454, 474 nm with AcO − and F − , respectively, indicating that ( R )‐ 1 can be applied to the detection of fluoride and acetate ions by naked eye. Receptor ( R )‐ 5 , containing a lipophilic dodecyl appendage at imidazolium nitrogen, exhibited larger fluorescent responses than ( R )‐ 1 . The ratio of fluorescence enhancement for ( R )‐ 5 with AcO − ( I 460 / I 369 =16) and F − ( I 485 / I 369 =11) was 32‐fold and 18‐fold over ( R )‐ 1 with AcO − ( I 454 / I 369 =0.5) and F − ( I 474 / I 369 =0.6), respectively. Less electron‐deficient benzimidazolium receptor ( R )‐ 2 only gave fluorescence enhance at 555 nm for F − . Only chelation enhanced quenching (CHEQ) effect was obtained in the case of mono‐imidazolium receptor ( R )‐ 4 . Furthermore, ( R )‐ 1 and ( R )‐ 5 displayed a remarkable binding ability for the t ‐Boc alanine anion with interesting enantioselectivity [ K L / K D =4.5 for ( R )‐ 1 and 4.1 for ( R )‐ 5 )], whereas only negligible enantioselectivity ability ( K L / K D =1.1) was obtained by using C 1 symmetric receptor ( R )‐ 4 .